Detection of fetal trisomy 9 mosaicism by noninvasive prenatal testing through maternal plasma DNA sequencing.

Noninvasive prenatal testing (NIPT) is widely used as a powerful screening tool to detect common aneuploidies. However, its application for detection of rare chromosomal abnormalities remains inconclusive. A 38-year-old woman (gravida 2, para 0) requested NIPT as a primary screening test for fetal aneuploidies at 13 weeks and 1 day of gestation. An unexpected Trisomy 9 (T9) abnormality was highly suspected. Amniocentesis was arranged for further diagnosis at 18 weeks of gestation. Final karyotyping reported 47,XX,+9 [18]/46,XX [12], indicating 60% T9 mosaicism. This case shows strong evidence that NIPT can be a powerful screening tool to detect rare fetal trisomies at very early gestation.

Lee CY ，Su HJ ，Cheng YT ，Ku YL ，Ngo YG ，Chen CM ，Ou YC ，Lee MC ，Shaw SWS ... -  《-》

Application of non-invasive prenatal testing in late gestation in a pregnancy associated with intrauterine growth restriction and trisomy 22 confined placental mosaicism.

We present the application of non-invasive prenatal testing (NIPT) in late gestation in a pregnancy associated with intrauterine growth restriction (IUGR) and trisomy 22 confined placental mosaicism (CPM). A 35-year-old pregnant woman underwent chorionic villus sampling (CVS) at 12 weeks of gestation. The pregnancy was conceived by in vitro fertilization and intracytoplasmic sperm injection. CVS revealed a karyotype of 47,XY,+22 in all of 15 cultured chorionic villi cells. Array comparative genomic hybridization analysis on uncultured chorionic villi revealed a result consistent with trisomy 22. The woman underwent amniocentesis at 17 weeks of gestation. Amniocentesis revealed a karyotype of 46,XY in all 20 colonies of cultured amniocytes. Additional polymorphic DNA marker analysis excluded uniparental disomy 22. The parental karyotypes were normal. Prenatal ultrasound at 23 weeks of gestation revealed fetal retrognathia, IUGR and a calcified placenta. NIPT at 27 weeks of gestation using maternal plasma cell-free DNA analysis showed a chromosome Z-score of 5.74 for chromosome 22 (the Z-score for each pair of chromosomes is defined as "increased" if >3), indicating an abnormal placenta with trisomy 22 CPM leading to IUGR in the fetus. At 36 weeks of gestation, a 1754-g male fetus was delivered with cleft palate and imperforate anus but no other phenotypic abnormalities. The cord blood had a karyotype of 46,XY (40/40 cells), the umbilical cord had a karyotype of 47,XY,+22[9]/46,XY[31], and the placental tissues had a karyotype of 47,XY,+22[15]/46,XY[25]. NIPT in late gestation is useful in detection of placental abnormality associated with CPM and IUGR but a normal karyotype at amniocentesis.

Chen CP ，Tsai C ，Lin MH ，Chern SR ，Chen SW ，Lai ST ，Chen WL ，Pan CW ，Wang W ... -  《-》

Detection of maternal uniparental disomy 9 in association with low-level mosaic trisomy 9 at amniocentesis in a pregnancy associated with intrauterine growth restriction, abnormal first-trimester screening result (low PAPP-A and low PlGF), maternal preecl

We present detection of maternal uniparental disomy (UPD) 9 in association with low-level mosaic trisomy 9 at amniocentesis in a pregnancy associated with intrauterine growth restriction (IUGR), an abnormal first-trimester maternal serum screening result, abnormal non-invasive prenatal testing (NIPT), maternal preeclampsia and a favorable outcome. A 37-year-old, primigravid woman underwent first-trimester maternal serum screening and NIPT at 11 weeks of gestation, which revealed a gene dosage increase in chromosome 9 and low levels of plasma protein-A (PAPP-A) and placental growth factor (PlGF) in maternal blood. The woman underwent amniocentesis at 16 weeks of gestation, which revealed a karyotype of 47,XX,+9[4]/46,XX[35] in cultured amniocytes. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed a result of arr [GRCh37] (9) × 3 [0.14] (X) × 2, compatible with mosaic trisomy 9. The parental karyotypes were normal. Repeat amniocentesis was performed at 20 weeks of gestation. The cultured amniocytes had a karyotype of 47,XX,+9[1]/46,XX[23]. The uncultured amniocytes had a mosaic trisomy 9 level of 10.7% (12/112 cells) by interphase fluorescence in situ hybridization (FISH), a mosaic trisomy 9 level of 10-14% (log2 ratio = 0.1) by aCGH, and maternal uniparental isodisomy 9 by polymorphic DNA marker analysis. Prenatal ultrasound revealed IUGR, and the mother had preeclampsia. At 29 weeks of gestation, a 1054-g phenotypically normal baby was delivered because of preterm labor. The cord blood and umbilical cord had the karyotype of 46, XX and maternal UPD 9 and isodisomy 9, while the placenta had trisomy 9 of maternal origin. Postnatal FISH anlaysis on 101 buccal mucosal cells and 100 urinary cells at age three months detected no trisomy 9 signals. The baby was doing well at age six months. Pregnancy with low-level mosaic trisomy 9 and maternal UPD 9 at amniocentesis can be associated with IUGR, maternal preeclampsia and a favorable outcome. Fetuses with maternal UPD 9 can be associated with an abnormal NIPT result concerning chromosome 9, an abnormal first-trimester maternal serum screening result (low PAPP-A and low PlGF) and mosaic trisomy 9 at amniocentesis.

Chen CP ，Chern SR ，Wu PS ，Chen SW ，Wu FT ，Chen LF ，Chen YY ，Wang W ... -  《-》

Non-invasive prenatal testing for fetal chromosomal abnormalities by low-coverage whole-genome sequencing of maternal plasma DNA: review of 1982 consecutive cases in a single center.

To review the performance of non-invasive prenatal testing (NIPT) by low-coverage whole-genome sequencing of maternal plasma DNA at a single center. The NIPT result and pregnancy outcome of 1982 consecutive cases were reviewed. NIPT was based on low coverage (0.1×) whole-genome sequencing of maternal plasma DNA. All subjects were contacted for pregnancy and fetal outcome. Of the 1982 NIPT tests, a repeat blood sample was required in 23 (1.16%). In one case, a conclusive report could not be issued, probably because of an abnormal vanished twin fetus. NIPT was positive for common trisomies in 29 cases (23 were trisomy 21, four were trisomy 18 and two were trisomy 13); all were confirmed by prenatal karyotyping (specificity=100%). In addition, 11 cases were positive for sex-chromosomal abnormalities (SCA), and nine cases were positive for other aneuploidies or deletion/duplication. Fourteen of these 20 subjects agreed to undergo further investigations, and the abnormality was found to be of fetal origin in seven, confined placental mosaicism (CPM) in four, of maternal origin in two and not confirmed in one. Overall, 85.7% of the NIPT-suspected SCA were of fetal origin, and 66.7% of the other abnormalities were caused by CPM. Two of the six cases suspected or confirmed to have CPM were complicated by early-onset growth restriction requiring delivery before 34 weeks. Fetal outcome of the NIPT-negative cases was ascertained in 1645 (85.15%). Three chromosomal abnormalities were not detected by NIPT, including one case each of a balanced translocation, unbalanced translocation and triploidy. There were no known false negatives involving the common trisomies (sensitivity=100%). Low-coverage whole-genome sequencing of maternal plasma DNA was highly accurate in detecting common trisomies. It also enabled the detection of other aneuploidies and structural chromosomal abnormalities with high positive predictive value.

Lau TK ，Cheung SW ，Lo PS ，Pursley AN ，Chan MK ，Jiang F ，Zhang H ，Wang W ，Jong LF ，Yuen OK ，Chan HY ，Chan WS ，Choy KW ... -  《-》

Discordant results between fetal karyotyping and non-invasive prenatal testing by maternal plasma sequencing in a case of uniparental disomy 21 due to trisomic rescue.

Uniparental disomy (UPD) is an uncommon chromosome condition, but UPD involving chromosome 21 is rarely reported. We reported here a case who had first trimester screening test for Down syndrome, chorionic villus sampling for fetal karyotyping, quantitative fluorescence polymerase chain reaction (QF-PCR), as well as non-invasive prenatal testing (NIPT) by maternal plasma sequencing. There were discordant results between fetal karyotyping and NIPT due to UPD 21combined with confined placental mosaicism of trisomy 21. This demonstrated that it is possible to detect placental mosaicism by NIPT, but further studies are required to confirm its sensitivity. Therefore, all positive NIPT results must be confirmed by conventional invasive test and karyotyping. QF-PCR has the additional benefit in diagnosing UPD.

Pan M ，Li FT ，Li Y ，Jiang FM ，Li DZ ，Lau TK ，Liao C ... -  《-》